The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent the work is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
A wireless full duplex technology implements that two communications nodes perform bidirectional signal transmission on a same time frequency resource. That is, a communications node that supports wireless full duplex can perform uplink/downlink transmission by using a same time frequency resource. However, when communication is performed by using the wireless full duplex technology, a transmit signal of the communications node interferes with a received signal of the communications node. Such interference is referred to as self-interference. A channel between a baseband transmission module and a baseband receiving module that are of the communications node is referred to as a baseband self-interference channel. Specifically, the baseband self-interference channel may include a cascade of the following: a transmit radio frequency channel response, a spatial channel, a leaked channel response of echo reflection of a radio frequency circuit, analog interference cancellation, and a channel response of a receive radio frequency channel. Further, if the communications node uses a circulator, the baseband self-interference channel may further include a channel response of the circulator.
To reduce impact caused by the self-interference on correct receiving of a desired signal, the communications node that supports the wireless full duplex needs to cancel the self-interference. A self-interference cancellation method includes one or more of the following: antenna isolation, analog interference cancellation, and digital interference cancellation.
A digital interference cancellation process includes: A communications node that supports wireless full duplex may estimate a response of a baseband self-interference channel of the communications node, and the communications node reconstructs baseband self-interference by using the estimated response of the baseband self-interference channel, and then subtracts the reconstructed baseband self-interference from actual baseband self-interference. A subtraction result is referred to as residual interference of the baseband self-interference channel, residual interference for short. Specifically, a subtraction result may be shown in formula 1.1:r=xrx−x′rx  Formula 1.1
where r indicates the residual interference, xrx indicates the actual baseband self-interference, and x′rx indicates the reconstructed baseband self-interference. Further, xrx=hx, where h indicates a response of the baseband self-interference channel, and x indicates a baseband transmit signal. x′rx=h′x, where h′ indicates the estimated response of the baseband self-interference channel.